1. Field of the Invention
This invention relates to cog rake bar screens and more particularly to guide rollers used with guide tracking on cog rake bar screens.
2. Description of Related Art
Cog rake bar screens are typically used in municipal and industrial coarse screening applications. The primary purpose of these screens is to retain and remove debris from channeled water flowing into water treatment plants, industrial sites, drainage facilities or overflow control facilities. Usually operated on float controls or timers these screens periodically remove debris which has accumulated on the upstream side of a bar rack mounted in the waste stream.
The mechanical cog rakes are guided by a guide track and may, for example, move in a counterclockwise path. Specifically, the mechanical cog rake may be lowered along the path and then move upward to remove the debris which has accumulated on the bar screen. After being raised, the cog rake may dump the debris into a trough.
The cog rake machines may utilize involute gearing and pin racks. As a result, they may require weldments internal to the side frames for the roller bearing guide tracking. During manufacturing, all guide tracking is generally shop fit and accurately welded into place inside the main side frame. If the frames are not accurately manufactured, the cog rake drive carriage operating within the guide may run very rough, vibrate significantly, or worse, potentially jam. If these machines do not run smoothly, then the excess vibration cannot only cause high stress loading on the sub-assemblies of the main rake carriage which operates within the guides, but can also lead to problems with the engagement of the drive carriage mounted rake teeth as they enter into the bar rack. Excess vibration may also cause the mounted rake teeth carriage to loose the debris the unit is attempting to remove.
Typically, standard spherical roller or ball bearing load runners which are packed with grease prior to installation along with spring loaded grease lubricators are used to help ensure that the guide rollers rotate freely thereby allowing the cog rake to smoothly move along the desired path. However, many applications may require that the cog rake mechanism itself be submerged into the wastewater being treated. The flow of the water or sewage may flush the grease from the bearings and may lead to the corrosion of the bearings. As a result, the bearings may lock up or otherwise fail to perform properly. It is therefore desirable to have a guide roller for use in a wastewater treatment facility in lieu of bearings which require greasing.